In a short statement, it announced that it was not just looking into Petrofac’s activities but also those of Petrofac’s officers, employees and agents “for suspected bribery, corruption and money laundering”.
The group confirmed in an announcement to the London Stock Exchange that it was being investigated and that chief executive Ayman Asfari and chief operating officer Marwan Chedid had both been questioned under caution by the SFO.
It also said that it had used Monaco-based Unaoil for local consultancy services primarily in Kazakhstan between 2002 and 2009.
In April last year, the group was forced to call in lawyers Freshfields Bruckhaus Deringer and auditors KPMG to investigate allegations that one of its former senior executives, who later joined the board of Unaoil, had paid out $2m (£1.55m) in alleged bribes to win an oil contract in Kuwait.
In August, Petrofac announced that the independent investigation had found “no evidence confirming the payment of bribes”.
The SFO launched a criminal investigation into Unaoil last year after Australian newspaper The Age accused the company of shady dealings that it had allegedly conducted on behalf of clients in order to win contracts around the world.
The scandal has also engulfed the UK subsidiaries of Swedish-Swiss engineering group ABB.
In February, the SFO announced that it was investigating their relationship with Unaoil and looking into “suspected offences of bribery and corruption”.